Posted by dold on February 13, 2010, 10:52 pm
Saying that typical sun time is 3-4 hours is no more reasonable than saying
it is 7.5 hours, unless there is a geographical reference supplied.
Someone else mentioned PVWatts version 2, but I prefer Version 1
Predicted solar energy available, based on real observation points around
the US and the world.
For my installation:
PVWatts for a nearby station, 4500 DC, 84%, 26 tilt, 214 az, 15.3 cents.
(kWh/m2/day) (kWh) ($)
Year 5.42 6777 1036.88
021506-021507 actual 6751 generated, 99.6% of NREL prediction.
http://cdold.home.mchsi.com/Solar-generation.htm $775 avoided in 2008
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5
Posted by Mike Brown on February 13, 2010, 4:01 am
I have a 5KW system located in Paso Robles, California, halfway
between San Francisco and Los Angeles. I've written an application
that show the production data for every day the system has been in
operation. Just go to the site and click on the app's screen image.
If you have a recent version of Java installed, the app will launch
and you can explore daily, weekly, yearly and lifetime data. Go to
the Custom Day tab and check the data for June 21 and December 21 and
you can see the shortest and longest power-generating days of the year
(although December is normally cloudy and rainy). My system peaks
around 35 KWH in the summer and drops to about 22 KWH on a clear day
in the winter. Let me know if you have any questions. I work for a
solar power company and can probably get you more in-depth data if you
need it. We use the PVWatts system from NREL among other tools to
predict our system's power output: http://rredc.nrel.gov/solar/codes_algs/P=
Posted by Harry B on February 13, 2010, 6:00 am
On 13/02/2010 3:01 PM, Mike Brown wrote:
Wow. You have some great info on this site. Congratulations.
I am trying to work out some of the scales on your graphs as to whether
you are talking gross or net, ow why your cumulative meter readings over
a year can have dips in them.
I will look more closely at a later stage.
Posted by stevey on February 14, 2010, 10:36 pm
I'm quite impressed with your web application monitoring your PV
performance, etc. I have been wanting to putup one for my Dad's
top site. What are the minimum provisioning to setup for your
It appears your array is tilted about 30Degrees, a near optimal angle
optimize production year-round. Instead of using the PVWatts, we at
Wattminder have deployed an instant PV performance benchmark
calculator at --www.wattminder.com. Please give it a try, you'll
Latitude and Longitude info., the rest you've already disclosed in
web page. Please give us a critique on this tool. We hope to revamp
it shortly for ease of use etc.
Your system should see better than 10 hours of good production --40KWh
in Summer. Please let me know how are the 25 modules connected?
in so many strings ? You may have a sub-optimal configuration.
Looking forward to your responses, and,
May the Sun always warm your face and your panels!
Posted by stevey on February 15, 2010, 2:51 pm
NREL --http://www.nrel.gov/gis/solar_map_development.html explains
amount of solar energy available at locations around the country.
http://www.nrel.gov/docs/fy02osti/30941.pdf has information about
production (by month) for a projected system.
Depending on locations, there is nominally 4 to 6 'average' good hours
Sun for PV purposes, i.e. if you multiply your system's DC capacity 5
5(hour) and by 360 (days) = 9000 KWh. of AC KWh of energy, over a